Superficial radiotherapy and volumetric modulated Arc therapy for skin cancers within hamartomatous skin in patient with PTEN mutation: A case report

Abstract

Phosphatase and tensin homolog (PTEN) gene acts as a tumour suppressor gene. Mutations of this gene are a step in the development of many cancers. Sufferers can have large fields of symptomatic hamartomatous skin change especially in sun exposed areas. RT has been reported to cause increased acute toxicity in this cohort. A 78-year-old fit male had a confirmed PTEN variant LRG_311t1 Exon 5, c353A>C. Symptomatic skin lesions of left frontal scalp and left nasal ala were confirmed on punch biopsy to be basal cell carcinoma (BCC) and he was referred for definitive radiotherapy (RT). He was treated with lesion based superficial radiotherapy to the left nasal ala to a total dose of 50 Gy in 25 fractions given at 5 fractions per week using a Xstrahl 300 machine via a 3cm circle applicator at 30cm source surface distance with a generating energy of 100 kV. The left frontal scalp was treated with a field-based volumetric modulated arc therapy technique to a planning target volume (PTV) of 74.8cm3 to 45 Gy with a simultaneous integrated boost PTV to 55 Gy of 4.1 cm3 to the BCC, all in 25 fractions. He developed the expected desquamation, erythema and mucositis within the nasal field and desquamation and erythema in the left temple. The PTEN mutation had no visible increase on the acute side effect profile compared with those without the mutation. After more than 6 months, the areas treated with RT remained clear of symptomatic hamartomatous skin change with no late toxicities. To our knowledge this is the longest benefit received of any treatment for fields of symptomatic hamartomatous skin change associated with PTEN mutation. It is also a report of not observing increased acute toxicity of RT in the definitive treatment of skin cancer in those with proven PTEN mutation. This one case adds evidence that definitive RT to skin may be delivered safely in this cohort. More studies with multiple patients with longer follow up are needed to confirm that those suffering with PTEN mutation can be safely and successfully treated with definitive RT for skin cancer and fields of symptomatic hamartomatous skin change with no increase in late effects.